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Add HTMLLayout fuzzer #454

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Add HTMLLayout fuzzer #454

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44a0813
Add HTMLLayout fuzzer
AdamKorcz Jan 17, 2025
95a57a3
fix options
AdamKorcz Jan 18, 2025
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2 changes: 1 addition & 1 deletion src/fuzzers/cpp/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@
# limitations under the License.
#

set(ALL_LOG4CXX_FUZZERS PatternLayoutFuzzer XMLLayoutFuzzer)
set(ALL_LOG4CXX_FUZZERS PatternLayoutFuzzer XMLLayoutFuzzer HTMLLayoutFuzzer)
set(LOG4CXX_CHAR "utf-8")

# Get the most recent Git commit ID
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89 changes: 89 additions & 0 deletions src/fuzzers/cpp/HTMLLayoutFuzzer.cpp
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@@ -0,0 +1,89 @@
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

#include "stdint.h"
#include <log4cxx/logstring.h>
#include <log4cxx/ndc.h>
#include <log4cxx/helpers/stringhelper.h>
#include <fuzzer/FuzzedDataProvider.h>
#include <log4cxx/mdc.h>
#include <log4cxx/htmllayout.h>

using namespace log4cxx;
using namespace log4cxx::helpers;
using namespace log4cxx::spi;

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
// Setup HTMLLayout
HTMLLayout layout;
log4cxx::helpers::Pool p;

FuzzedDataProvider fdp(data, size);

// Optional locationinfo
if (fdp.ConsumeBool()) {
layout.setOption(LOG4CXX_STR("LOCATIONINFO"), LOG4CXX_STR("true"));
}
// Optional threadinfo
if (fdp.ConsumeBool()) {
LOG4CXX_DECODE_CHAR(title, fdp.ConsumeRandomLengthString());
layout.setOption(LOG4CXX_STR("TITLE"), title);
}

// Header
if (fdp.ConsumeBool()) {
std::string headerStr = fdp.ConsumeRandomLengthString();
layout.appendHeader(LOG4CXX_STR(headerStr), p);
}

// Create random strings we need later
std::string key1 = fdp.ConsumeRandomLengthString();
std::string val1 = fdp.ConsumeRandomLengthString();
std::string key2 = fdp.ConsumeRandomLengthString();
std::string val2 = fdp.ConsumeRandomLengthString();
std::string key3 = fdp.ConsumeRandomLengthString();
std::string val3 = fdp.ConsumeRandomLengthString();
std::string key4 = fdp.ConsumeRandomLengthString();
std::string val4 = fdp.ConsumeRandomLengthString();
std::string ndcMessage = fdp.ConsumeRandomLengthString();
std::string loggerStr = fdp.ConsumeRandomLengthString();
std::string content = fdp.ConsumeRemainingBytesAsString();
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@swebb2066 swebb2066 Jan 18, 2025 •
edited
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I believe you need to provide a maximum length to ConsumeRandomLengthString or all subsequent calls will return an empty string.

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@AdamKorcz AdamKorcz Jan 18, 2025 •
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That is not the case. The fuzzer determines the length of the string in a deterministic manner. It can consist of the entire test case, but those odd cases are fine. Ref the doc:

"ConsumeRandomLengthString method returns a std::string as well, but its length is derived from the fuzz input and typically is hard to predict, though always deterministic. The caller can provide the max length argument."

https://github.com/google/fuzzing/blob/master/docs/split-inputs.md#methods-for-extracting-sequences-of-bytes

I also tested it locally and found that the non-first invocations of fdp.ConsumeRandomLengthString() do indeed generate strings.

The one that should always be last is ConsumeRemainingBytesAsString(). If it is not, then the remaining attempts to generate strings will yield empty strings like you say.

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Unfortunately the documentation (and the ConsumeRandomLengthString function name) is missleading. When I build XMLLayoutFuzzer with an extra line log4cxx::helpers::LogLog::debug(result); I get this result (for example):

log4cxx: <log4j:event logger="com.example.bar" timestamp="1737242190330" level="INFO" thread="0x728374e74000">
<log4j:message><![CDATA[]]></log4j:message>
<log4j:NDC><![CDATA[<envelope><faultstring><![CDATA[The EffectiveDate]]>]]&gt;<![CDATA[</faultstring><envelope>]]></log4j:NDC>
<log4j:locationInfo class="" method="LLVMFuzzerTestOneInput" file="/home/stephen/source/logging-log4cxx/src/fuzzers/cpp/XMLLayoutFuzzer.cpp" line="45"/>
<log4j:properties>
<log4j:data name=";▒" value=""/>
<log4j:data name=";▒" value=""/>
</log4j:properties>
</log4j:event>

Note also there is bug in XMLLayoutFuzzer. I believe

        // Set MDC
        log4cxx::MDC::put(key1, key2);

was supposed to be:

        // Set MDC
        log4cxx::MDC::put(key2, val2);


log4cxx::LogString logger = LOG4CXX_STR(loggerStr);
log4cxx::LevelPtr level = log4cxx::Level::getInfo();
log4cxx::NDC::push(ndcMessage);
log4cxx::spi::LoggingEventPtr event = log4cxx::spi::LoggingEventPtr(
new log4cxx::spi::LoggingEvent(
logger, level, LOG4CXX_STR(content), LOG4CXX_LOCATION));

// Set properties
event->setProperty(LOG4CXX_STR(key1), LOG4CXX_STR(val1));
event->setProperty(LOG4CXX_STR(key2), LOG4CXX_STR(val2));

// Set MDC
log4cxx::MDC::put(key3, val3);
log4cxx::MDC::put(key4, val4);

// Call the target API
log4cxx::LogString result;
layout.format(result, event, p);

// Clean up
log4cxx::NDC::clear();
log4cxx::MDC::clear();
return 0;
}